Areal density represents the amount of information bits on a surface. In Hard Disk Drives (HDDs), areal density is limited by the superparamagnetic limit (the number of information bits that may fit on a given surface, wherein the bits are separated from each other enough not to affect or be effected by the neighboring magnetic bits). High temperatures may adversely affect the superparamagnetic limit and the HDD thus may fail. HDDs may also fail if subjected to physical impact, radiation, electromagnetic fields, abrasive surfaces, or external magnetic forces. Solid State Devices (SSD) may also fail for many reasons, such as being subjected to radiation.
Most central processing units are labeled in terms of their clock rate (the rate at which the processor executes instructions). The current highest rate is about 6 or 7 GHz or 6-7 gigacycles per second. The clock cycle toggles between a logical 0 state and a logical 1 state.